Gosu Cave

If the phrase "subterranean palace" piques your curiosity, consider paying an exploratory visit to North Chungcheong Province's Gosu Cave. Across the river from Danyang, this sizable limestone cavern descends 1,298 m (4,259 ft) into the Earth's crust, displaying five and a half kilometers of incredible stalactite and stalagmite formations that can't help but leave an impression. Though the path for visitors only covers about 1/3 of the total length, it's more than capable of eliciting a few "oohs" and "ahhs" via unique geological figures like Lion Rock, Octopus Rock and the Virgin Mary rock itself. Remember to bring something long-sleeve (the interior of Gosu stays an unwavering 15°C year-round), and be prepared for a few fairly tight spaces and more than a few stairs. All in all, though, that's a small price to pay for such a memorable experience.

Location:Danyang-gun, South Korea

Note:This one goes out to all you history buffs out there: prehistoric stone artifacts unearthed near Gosu Cave's entrance back in the 1970's indicate its ties to early South Korean civilization, making a visit to this national monument an excursion into both the country's natural and ancestral past.